JP6305391B2 - Charge transport materials, host materials, thin films, and organic light emitting devices - Google Patents

Description

  The present invention relates to a compound useful as a charge transport material or a host material, a thin film formed using the compound, and an organic light emitting device.

  Researches for increasing the light emission efficiency of organic light emitting devices such as organic electroluminescence devices (organic EL devices) are being actively conducted. In particular, various efforts have been made to increase the light emission efficiency by newly developing and combining electron transport materials, hole transport materials, light emitting materials, host materials, and the like constituting the organic electroluminescence element. Among them, research on organic light-emitting devices using a compound containing a cyclotriphosphazene ring can also be found.

For example, Non-Patent Document 1 describes that a compound represented by the following general formula is useful as a host material for a blue phosphorescent material. Non-Patent Document 1 specifically describes a compound in which a 3,5-dimethylphenyl group is bonded to a cyclotriphosphazene ring, a compound in which a 4-methoxyphenyl group is bonded, and a compound in which an unsubstituted phenyl group is bonded. Yes. Non-Patent Document 1 describes that the decomposition temperature of these compounds is 280 to 330 ° C., and the T1 level (lowest excited triplet energy level) is more than 3.0 eV.

Patent Document 1 describes that a compound represented by the following general formula is useful as a host material for a phosphorescent material or a fluorescent material. In the following general formula, Y is an aryl group, heteroaryl group, carbazolyl group or azacarbazolyl group, and is defined to be bonded to the phosphorus atom of the cyclotriphosphazene ring via a carbon atom. Patent Document 1 specifically describes compounds in which Y is a 4- (carbazol-9-yl) phenyl group or an N-methylcarbazol-3-yl group. However, no compound is described which is bonded to the phosphorus atom of the cyclotriphosphazene ring via a nitrogen atom.

  Non-Patent Document 2 describes one compound that is bonded to the phosphorus atom of the cyclotriphosphazene ring via a nitrogen atom. Non-Patent Document 2 discusses the light emission characteristics of a compound in which Y in the above general formula is a carbazol-9-yl group. However, Non-Patent Document 2 does not describe the usefulness of this compound as a charge transport material or as a host material.

Pamela Schrogel et al., Chem. Mater., 2011, 23 (22), 4947-4953 Yu.T.Kononenko et al., Journal of Molecular Liquids 127 (2006) 118-120

Special table 2011-525047 gazette

  Thus, it has been proposed so far to use a compound having a cyclotriphosphazene ring for a light-emitting element. Although the compounds described in Non-Patent Document 1 and Patent Document 1 certainly have a high T1 level, it is difficult to say that their thermal stability and luminous efficiency are sufficiently high. If the thermal stability is not sufficient, there are problems such as restrictions in the process for producing the organic light emitting device and the inability to provide a desired device. If the luminous efficiency cannot be sufficiently increased, the utility value as a charge transporting material or a host material will be greatly impaired. In consideration of such problems of the prior art, the present inventors have intensively studied for the purpose of improving the thermal stability and luminous efficiency of a compound having a cyclotriphosphazene ring.

  As a result of diligent studies to achieve the above object, the present inventors have found that a compound having a specific structure has a high T1 level and excellent thermal stability and is useful as a charge transport material. It was. In addition, the present inventors found that the compound is useful as a host material for blue light emitting materials, and can greatly improve the light emission efficiency and luminance of the organic light emitting device. Based on these findings, the present inventors have provided the following present invention as means for solving the above problems.

［一般式（１）において、Ｒ¹〜Ｒ⁶は各々独立に下記一般式（２）で表される基である。

［一般式（２）において、Ｒ⁷は置換もしくは無置換のアリール基、または置換もしくは無置換のアラルキル基を表す。Ｒ¹¹〜Ｒ¹⁵は各々独立に水素原子または置換基を表す。Ｒ⁷とＲ¹¹、Ｒ¹¹とＲ¹²、Ｒ¹²とＲ¹³、Ｒ¹³とＲ¹⁴、Ｒ¹⁴とＲ¹⁵は互いに結合して環状構造を形成していてもよい。］
［２］ 一般式（１）のＲ¹〜Ｒ⁶がすべて同一であることを特徴とする［１］に記載の電荷輸送材料。
［３］ 一般式（１）のＲ¹〜Ｒ⁶が下記一般式（３）〜（７）のいずれかで表される基であることを特徴とする［１］または［２］に記載の電荷輸送材料。

［一般式（３）〜（７）において、Ｒ²¹〜Ｒ³⁸、Ｒ⁴¹〜Ｒ⁴⁸、Ｒ⁵¹〜Ｒ⁵⁸、Ｒ⁶¹〜Ｒ⁶⁵、Ｒ⁷¹〜Ｒ⁷⁹は、各々独立に水素原子または置換基を表す。Ｒ²¹とＲ²²、Ｒ²²とＲ²³、Ｒ²³とＲ²⁴、Ｒ²⁴とＲ²⁵、Ｒ²⁵とＲ²⁶、Ｒ²⁶とＲ²⁷、Ｒ²⁷とＲ²⁸、Ｒ²⁸とＲ²⁹、Ｒ²⁹とＲ³⁰、Ｒ³¹とＲ³²、Ｒ³²とＲ³³、Ｒ³³とＲ³⁴、Ｒ³⁵とＲ³⁶、Ｒ³⁶とＲ³⁷、Ｒ³⁷とＲ³⁸、Ｒ⁴¹とＲ⁴²、Ｒ⁴²とＲ⁴³、Ｒ⁴³とＲ⁴⁴、Ｒ⁴⁵とＲ⁴⁶、Ｒ⁴⁶とＲ⁴⁷、Ｒ⁴⁷とＲ⁴⁸、Ｒ⁵¹とＲ⁵²、Ｒ⁵²とＲ⁵³、Ｒ⁵³とＲ⁵⁴、Ｒ⁵⁵とＲ⁵⁶、Ｒ⁵⁶とＲ⁵⁷、Ｒ⁵⁷とＲ⁵⁸、Ｒ⁶¹とＲ⁶²、Ｒ⁶²とＲ⁶³、Ｒ⁶³とＲ⁶⁴、Ｒ⁶⁴とＲ⁶⁵、Ｒ⁵⁴とＲ⁶¹、Ｒ⁵⁵とＲ⁶⁵、Ｒ⁷¹とＲ⁷²、Ｒ⁷²とＲ⁷³、Ｒ⁷³とＲ⁷⁴、Ｒ⁷⁴とＲ⁷⁵、Ｒ⁷⁶とＲ⁷⁷、Ｒ⁷⁷とＲ⁷⁸、Ｒ⁷⁸とＲ⁷⁹は互いに結合して環状構造を形成していてもよい。］
［４］ 一般式（１）のＲ¹〜Ｒ⁶が前記一般式（３）で表される基であることを特徴とする［３］に記載の電荷輸送材料。
［５］ 一般式（１）のＲ¹〜Ｒ⁶が下記一般式（８）で表される基であることを特徴とする［３］または［４］に記載の電荷輸送材料。

［一般式（８）において、Ｒ²¹〜Ｒ²⁴、Ｒ²⁷〜Ｒ³⁰は、各々独立に水素原子または置換基を表す。Ｒ²¹とＲ²²、Ｒ²²とＲ²³、Ｒ²³とＲ²⁴、Ｒ²⁷とＲ²⁸、Ｒ²⁸とＲ²⁹、Ｒ²⁹とＲ³⁰は互いに結合して環状構造を形成していてもよい。］
［６］ 下記の構造を有する化合物からなることを特徴とする［５］に記載の電荷輸送材料。

［上の構造において、水素原子は置換基で置換されていてもよい。］
［７］ ［１］〜［６］のいずれか１項に記載の電荷輸送材料からなることを特徴とするホスト材料。
［８］ 青色発光材料用であることを特徴とする［７］に記載のホスト材料。
［９］ ［７］に記載のホスト材料と発光材料を含むことを特徴とする薄膜。
［１０］ 前記発光材料が青色発光材料であることを特徴とする［９］に記載の薄膜。
［１１］ ［１］〜［６］のいずれか１項に記載の電荷輸送材料を用いたことを特徴とする有機発光素子。
［１２］ 前記電荷輸送材料をホスト材料として発光層に用いたことを特徴とする［１１］に記載の有機発光素子。
［１３］ リン光を放射することを特徴とする［１１］または［１２］に記載の有機発光素子。
［１４］ 遅延蛍光を放射することを特徴とする［１１］または［１２］に記載の有機発光素子。
［１５］ 有機エレクトロルミネッセンス素子であることを特徴とする［１１］〜［１４］のいずれか１項に記載の有機発光素子。[1] A charge transport material comprising a compound represented by the following general formula (1).

[In General Formula (1), R ^{1 to} R ⁶ are each independently a group represented by the following General Formula (2).

[In the general formula (2), R ⁷ represents a substituted or unsubstituted aryl group or a substituted or unsubstituted aralkyl group. R ^{11 to} R ¹⁵ each independently represents a hydrogen atom or a substituent. R ⁷ and R ¹¹ , R ¹¹ and R ¹² , R ¹² and R ¹³ , R ¹³ and R ¹⁴ , and R ¹⁴ and R ¹⁵ may be bonded to each other to form a cyclic structure. ]
[2] The charge transport material according to [1], wherein R ^{1 to} R ^{6 in} the general formula (1) are all the same.
[3] As described in [1] or [2], R ^{1 to} R ^{6 in} the general formula (1) are groups represented by any of the following general formulas (3) to (7) Charge transport material.

[In the general formulas (3) to (7), R ^{21 to} R ³⁸ , R ^{41 to} R ⁴⁸ , R ^{51 to} R ⁵⁸ , R ^{61 to} R ⁶⁵ , R ^{71 to} R ⁷⁹ are each independently a hydrogen atom or a substituent. Represents a group. R ²¹ and R ²² , R ²² and R ²³ , R ²³ and R ²⁴ , R ²⁴ and R ²⁵ , R ²⁵ and R ²⁶ , R ²⁶ and R ²⁷ , R ²⁷ and R ²⁸ , R ²⁸ and R ²⁹ , R ²⁹ and R ^30, R ³¹ and R ^32, R ³² and R ^33, R ³³ and R ^34, R ³⁵ and R ^36, R ³⁶ and R ^37, R ³⁷ and R ^38, R ⁴¹ and R ^42, R ⁴² and R ⁴³ , R ⁴³ and R ⁴⁴ , R ⁴⁵ and R ⁴⁶ , R ⁴⁶ and R ⁴⁷ , R ⁴⁷ and R ⁴⁸ , R ⁵¹ and R ⁵² , R ⁵² and R ⁵³ , R ⁵³ and R ⁵⁴ , R ⁵⁵ and R ⁵⁶ , ^R56 and ^R57 , ^R57 and ^R58 , ^R61 and ^R62 , ^R62 and ^R63 , ^R63 and ^R64 , ^R64 and ^R65 , ^R54 and ^R61 , ^R55 and ^R65 , ^R71 And R ⁷² , R ⁷² and R ⁷³ , R ⁷³ and R ⁷⁴ , R ⁷⁴ and R ⁷⁵ , R ⁷⁶ and R ⁷⁷ , R ⁷⁷ and R ⁷⁸ , R ⁷⁸ and R ⁷⁹ are bonded to each other to form a cyclic structure. May be. ]
[4] The charge transport material according to [3], wherein R ^{1 to} R ^{6 in} the general formula (1) are groups represented by the general formula (3).
[5] The charge transport material according to [3] or [4], wherein R ^{1 to} R ^{6 in} the general formula (1) are groups represented by the following general formula (8).

[In General formula (8), R < ²¹ > -R < ²⁴ >, R < ²⁷ > -R < ³⁰ > represents a hydrogen atom or a substituent each independently. R ²¹ and R ²² , R ²² and R ²³ , R ²³ and R ²⁴ , R ²⁷ and R ²⁸ , R ²⁸ and R ²⁹ , and R ²⁹ and R ³⁰ may be bonded to each other to form a cyclic structure. ]
[6] The charge transport material according to [5], comprising a compound having the following structure.

[In the above structure, the hydrogen atom may be substituted with a substituent. ]
[7] A host material comprising the charge transport material according to any one of [1] to [6].
[8] The host material according to [7], which is for a blue light emitting material.
[9] A thin film comprising the host material according to [7] and a light emitting material.
[10] The thin film according to [9], wherein the light emitting material is a blue light emitting material.
[11] An organic light-emitting device using the charge transport material according to any one of [1] to [6].
[12] The organic light-emitting device according to [11], wherein the charge transport material is used as a host material in a light-emitting layer.
[13] The organic light-emitting element according to [11] or [12], which emits phosphorescence.
[14] The organic light-emitting device according to [11] or [12], which emits delayed fluorescence.
[15] The organic light-emitting device according to any one of [11] to [14], which is an organic electroluminescence device.

  The compound represented by the general formula (1) is useful as a charge transport material. It is also useful as a host material when a light emitting material is used as a dopant. By using the host material of the present invention, it is possible to provide an organic light emitting device having high luminous efficiency and high maximum luminance.

It is a schematic sectional drawing which shows the layer structural example of an organic electroluminescent element. 2 is an emission spectrum of the organic photoluminescence device of Example 1. 2 is an emission spectrum of organic electroluminescence elements of Example 2 and Comparative Example 1. It is a graph which shows the current density-voltage-luminance characteristic of the organic electroluminescent element of Example 2 and Comparative Example 1. It is a graph which shows the current density-external quantum efficiency characteristic of the organic electroluminescent element of Example 2 and Comparative Example 1. It is a graph which shows the current density-voltage-luminance characteristic of the organic electroluminescent element of Example 2 and Comparative Example 2. It is a graph which shows the current density-external quantum efficiency characteristic of the organic electroluminescent element of Example 2 and Comparative Example 2. 3 is an emission spectrum of organic electroluminescence elements of Example 3 and Comparative Example 3. It is a graph which shows the current density-voltage-luminance characteristic of the organic electroluminescent element of Example 3 and Comparative Example 3. It is a graph which shows the current density-external quantum efficiency characteristic of the organic electroluminescent element of Example 3 and Comparative Example 3.

Hereinafter, the contents of the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments and specific examples of the present invention, but the present invention is not limited to such embodiments and specific examples. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value. In addition, the isotope species of the hydrogen atom present in the molecule of the compound used in the present invention is not particularly limited. For example, all the hydrogen atoms in the molecule may be ¹ H, or a part or all of them are ² H. (Deuterium D) may be used.

[Compound represented by general formula (1)]
The charge transport material of the present invention is characterized by comprising a compound represented by the following general formula (1).

In the general formula (1), R ^{1 to} R ⁶ are each independently a group represented by the following general formula (2).

In the general formula (2), R ⁷ represents a substituted or unsubstituted aryl group or a substituted or unsubstituted aralkyl group.
The aromatic ring constituting the aryl group herein may be a single ring or a condensed ring, and specific examples include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring. The aryl group preferably has 6 to 40 carbon atoms, more preferably 6 to 20 carbon atoms, and still more preferably 6 to 14 carbon atoms. Specific examples of the aryl group include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 1-anthracenyl group, a 2-anthracenyl group, and a 9-anthracenyl group.

  Moreover, the aralkyl group here means an alkyl group substituted with at least one aryl group, and the alkyl part may be linear or branched. 1-20 are preferable, as for carbon number of an alkyl part, 1-10 are more preferable, and 1-5 are more preferable. The aromatic ring constituting the aryl moiety may be a single ring or a condensed ring. For specific examples and preferred carbon numbers, the specific examples and preferred ranges of the above aryl groups can be referred to. The aryl group constituting the aralkyl group is preferably bonded to the 1-position of the alkyl group. Moreover, when there are two or more aryl groups constituting the aralkyl group, they may be the same or different from each other. Specific examples of the aralkyl group include phenylmethyl group, 1-phenylethyl group, 1-phenylpropyl group, 1-phenylbutyl group, 1-phenylpentyl group, 1-phenylhexyl group, naphthalen-1-ylmethyl group, 1- (Naphthalen-1-yl) ethyl group, naphthalen-2-ylmethyl group, 1- (naphthalen-2-yl) ethyl group can be exemplified.

In the general formula (2), R ⁷ and R ¹¹ may be bonded to each other to form a cyclic structure. The formed cyclic structure is preferably a 5- to 7-membered ring, and more preferably a 5- or 6-membered ring. The formed ring skeleton-forming atom may or may not contain a hetero atom other than the nitrogen atom to which R ⁷ and R ¹¹ are bonded. When it contains, it can contain a nitrogen atom, a sulfur atom, and an oxygen atom, for example. Examples of preferred cyclic structures include 1,4-oxazine ring, 1,4-thiazine ring, pyrazine ring, and pyrrole ring. When forming a pyrazine ring, it is preferable that a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group is bonded to the nitrogen atom at the 4-position, and a substituted or unsubstituted aryl group is bonded. More preferably, a substituted or unsubstituted phenyl group is more preferably bonded.

In General formula (2), R < ¹¹ > -R < ¹⁵ > represents a hydrogen atom or a substituent each independently. The number of substituents is not particularly limited, and all of R ^{11 to} R ¹⁵ may be unsubstituted (that is, hydrogen atoms). When two or more of R ^{11 to} R ¹⁵ are substituents, the plurality of substituents may be the same as or different from each other. Examples of the substituent that R ^{11 to} R ¹⁵ can take and the substituent that the aryl group or aralkyl group represented by R ⁷ can take include, for example, a hydroxy group, a halogen atom, a cyano group, an alkyl group having 1 to 20 carbon atoms, and 1 carbon atom. -20 alkoxy group, C1-C20 alkylthio group, C1-C20 alkyl-substituted amino group, C2-C20 acyl group, C6-C40 aryl group, C3-C40 Heteroaryl group, C2-C10 alkenyl group, C2-C10 alkynyl group, C2-C10 alkoxycarbonyl group, C1-C10 alkylsulfonyl group, C1-C10 haloalkyl group An amide group, an alkylamide group having 2 to 10 carbon atoms, a trialkylsilyl group having 3 to 20 carbon atoms, a trialkylsilylalkyl group having 4 to 20 carbon atoms, and 5 to 20 carbon atoms Trialkyl silyl alkenyl group, and the like trialkylsilyl alkynyl group and a nitro group having 5 to 20 carbon atoms. Among these specific examples, those that can be substituted with a substituent may be further substituted. More preferred substituents are a halogen atom, a cyano group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 40 carbon atoms, carbon A substituted or unsubstituted heteroaryl group having 3 to 40 carbon atoms and a dialkyl-substituted amino group having 1 to 20 carbon atoms. More preferable substituents are a fluorine atom, a chlorine atom, a cyano group, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms, and a substituted group having 6 to 15 carbon atoms. Or it is an unsubstituted aryl group, a C3-C12 substituted or unsubstituted heteroaryl group.

In the general formula (2), R ¹¹ and R ¹² , R ¹² and R ¹³ , R ¹³ and R ¹⁴ , and R ¹⁴ and R ¹⁵ may be bonded to each other to form a cyclic structure. The cyclic structure may be an aromatic ring or an alicyclic ring, may contain a hetero atom, and the cyclic structure may be a condensed ring of two or more rings. The hetero atom here is preferably selected from the group consisting of a nitrogen atom, an oxygen atom and a sulfur atom. Examples of cyclic structures formed include benzene ring, naphthalene ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring, pyrrole ring, imidazole ring, pyrazole ring, triazole ring, imidazoline ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, and cyclohexadiene ring, a cyclohexene ring, Shikuropen Te down ring, cycloheptatriene ring, cycloheptadiene ring, etc. Shikurohepu te down ring.

All of R ^{1 to} R ^{6 in} the general formula (1) may be the same or different. Moreover, a part may be the same. For example, R ¹ and R ² are the same, R ³ and R ⁴ are the same, R ⁵ and R ⁶ are the same, or R ¹ , R ³ and R ⁵ are the same, R ² and A case where R ⁴ and R ⁶ are the same can be mentioned. If all of R ^{1 to} R ⁶ are the same, there is an advantage that the synthesis is easy.

R ^{1 to} R ^{6 in} the general formula (1) are preferably groups represented by any of the following general formulas (3) to (7).

In the general formulas (3) to (7), R ^{21 to} R ³⁸ , R ^{41 to} R ⁴⁸ , R ^{51 to} R ⁵⁸ , R ^{61 to} R ⁶⁵ , and R ^{71 to} R ⁷⁹ are each independently a hydrogen atom or a substituent. Represents. For the explanation and preferred ranges of the substituents mentioned here, the explanations and preferred ranges of the substituents that can be taken by the above R ^{11 to} R ¹⁵ can be referred to. The number of substituents in general formulas (3) to (7) is not particularly limited. It is also preferred that all are unsubstituted (ie hydrogen atoms). Moreover, when there are two or more substituents in each of the general formulas (3) to (7), these substituents may be the same or different. When a substituent is present in the general formulas (3) to (7), the substituent is preferably any one of R ^{22 to} R ²⁴ and R ^{27 to} R ²⁹ if the substituent is the general formula (3). In general formula (4), any of R ^{32 to} R ³⁷ is preferable, and in general formula (5), any of R ^{42 to} R ⁴⁷ is preferable, and general formula (6) Is preferably R ⁵² , R ⁵³ , R ⁵⁶ , R ⁵⁷ , R ^{62 to} R ⁶⁴ , and any one of R ^{72 to} R ⁷⁴ , R ⁷⁷ , and R ⁷⁸ is the general formula (7). It is preferable that

In the general formulas (3) to (7), R ²¹ and R ²² , R ²² and R ²³ , R ²³ and R ²⁴ , R ²⁴ and R ²⁵ , R ²⁵ and R ²⁶ , R ²⁶ and R ²⁷ , R ²⁷ and R ²⁸ , R ²⁸ and R ²⁹ , R ²⁹ and R ³⁰ , R ³¹ and R ³² , R ³² and R ³³ , R ³³ and R ³⁴ , R ³⁵ and R ³⁶ , R ³⁶ and R ³⁷ , R ³⁷ and R ^{38 R41} and ^R42 , ^R42 and ^R43 , ^R43 and ^R44 , ^R45 and ^R46 , ^R46 and ^R47 , ^R47 and ^R48 , ^R51 and ^R52 , ^R52 and ^R53 , R ⁵³ and R ⁵⁴ , R ⁵⁵ and R ⁵⁶ , R ⁵⁶ and R ⁵⁷ , R ⁵⁷ and R ⁵⁸ , R ⁶¹ and R ⁶² , R ⁶² and R ⁶³ , R ⁶³ and R ⁶⁴ , R ⁶⁴ and R ⁶⁵ , R ⁵⁴ and ^R61 , ^R55 and ^R65 , ^R71 and ^R72 , ^R72 and ^R73 , ^R73 and ^R74 , ^R74 and ^R75 , ^R76 and ^R77 , ^R77 and ^R78 , ^R78 and ^R79 May be bonded to each other to form a cyclic structure. For the explanation and preferred examples of the cyclic structure, reference can be made to the explanation and preferred examples of the cyclic structure formed by combining R ¹¹ and R ¹² in the general formula (2).

All of R ^{1 to} R ^{6 in} the general formula (1) are preferably groups represented by any one of the general formulas (3) to (7). For example, the case where all of R ^{1 to} R ⁶ are groups represented by the general formula (3) can be preferably exemplified. At this time, all of R ^{1 to} R ⁶ may be the same group or different groups.

R ^{1 to} R ^{6 in} the general formula (1) are preferably groups represented by the following general formula (8). The general formula (8) is a structure in which R ²⁵ and R ^{26 in} the general formula (3) are bonded to each other by a single bond.

In General formula (8), R < ²¹ > -R < ²⁴ >, R < ²⁷ > -R < ³⁰ > represents a hydrogen atom or a substituent each independently. R ²¹ and R ²² , R ²² and R ²³ , R ²³ and R ²⁴ , R ²⁷ and R ²⁸ , R ²⁸ and R ²⁹ , and R ²⁹ and R ³⁰ may be bonded to each other to form a cyclic structure. For the explanation of the substituent and the explanation of the cyclic structure, the corresponding descriptions in the general formula (2) and the general formula (3) can be referred to.

Preferable examples of the compound represented by the general formula (1) include compounds having the following structure. A hydrogen atom present in the following structure may be substituted with a substituent. For the explanation and preferred range of the substituent, the corresponding descriptions in general formula (2) and general formula (3) can be referred to.

  Below, the specific example of a compound represented by General formula (1) is illustrated. However, the compound represented by the general formula (1) that can be used in the present invention should not be limitedly interpreted by these specific examples.

The molecular weight of the compound represented by the general formula (1) is, for example, 1500 or less when the organic layer containing the compound represented by the general formula (1) is intended to be formed by vapor deposition. Preferably, it is preferably 1200 or less, more preferably 1000 or less, and even more preferably 800 or less. The lower limit of the molecular weight is the molecular weight of the minimum compound represented by the general formula (1).
The compound represented by the general formula (1) may be formed by a coating method regardless of the molecular weight. If a coating method is used, a film can be formed even with a compound having a relatively large molecular weight.

By applying the present invention, it is also conceivable to use a compound containing a plurality of structures represented by the general formula (1) in the molecule as a light emitting material.
For example, it is conceivable to use a polymer obtained by previously polymerizing a polymerizable group in the structure represented by the general formula (1) and polymerizing the polymerizable group as a light emitting material. Specifically, by preparing a monomer containing a polymerizable functional group in any of R ^{1 to} R ⁶ of the general formula (1) and polymerizing it alone or copolymerizing with other monomers, It is conceivable to obtain a polymer having a repeating unit and use the polymer as a light emitting material. Alternatively, it is also possible to obtain a dimer or trimer by coupling compounds having a structure represented by the general formula (1) and use them as a light emitting material.

Examples of the polymer having a repeating unit containing a structure represented by the general formula (1) include a polymer containing a structure represented by the following general formula (9) or (10).

In the general formulas (9) and (10), Q represents a group including the structure represented by the general formula (1), and L ¹ and L ² represent a linking group. Carbon number of a coupling group becomes like this. Preferably it is 0-20, More preferably, it is 1-15, More preferably, it is 2-10. And preferably has a structure represented by - linking group -X ¹¹ -L ^11. Here, X ¹¹ represents an oxygen atom or a sulfur atom, and is preferably an oxygen atom. L ¹¹ represents a linking group, preferably a substituted or unsubstituted alkylene group, or a substituted or unsubstituted arylene group, and a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms, or a substituted or unsubstituted group A phenylene group is more preferable.
In the general formulas (9) and (10), R ¹⁰¹ , R ¹⁰² , R ¹⁰³ and R ¹⁰⁴ each independently represent a substituent. Preferably, it is a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 6 carbon atoms, or a halogen atom, more preferably an unsubstituted alkyl group having 1 to 3 carbon atoms. An unsubstituted alkoxy group having 1 to 3 carbon atoms, a fluorine atom, and a chlorine atom, and more preferably an unsubstituted alkyl group having 1 to 3 carbon atoms and an unsubstituted alkoxy group having 1 to 3 carbon atoms.
The linking group represented by L ¹ and L ² is any ^one of R ^{1 to} R ⁶ of the structure of the general formula (1) constituting Q, R ⁷ , R ^{11 to} R ¹⁵ of the structure of the general formula (2). Any one of R ^{21 to} R ³⁰ of the structure of the general formula (3), any of R ^{31 to} R ³⁸ of the structure of the general formula (4), R ^{41 to} R of the structure of the general formula (5) Any one of ⁴⁸ , R ^{51 to} R ⁵⁸ and R ^{61 to} R ⁶⁵ in the structure of the general formula (6), and R ^{71 to} R ^{78 in} the structure of the general formula (7). . Two or more linking groups may be linked to one Q to form a crosslinked structure or a network structure.

Specific examples of the structure of the repeating unit include structures represented by the following formulas (11) to (14).

In the polymer having a repeating unit containing these formulas (11) to (14), a hydroxy group is introduced into any ^one of R ^{1 to} R ^{6 in} the structure of the general formula (1), and this is used as a linker as described below. It can be synthesized by reacting a compound to introduce a polymerizable group and polymerizing the polymerizable group.

  The polymer containing the structure represented by the general formula (1) in the molecule may be a polymer composed only of repeating units having the structure represented by the general formula (1), or other structures may be used. It may be a polymer containing repeating units. The repeating unit having a structure represented by the general formula (1) contained in the polymer may be a single type or two or more types. Examples of the repeating unit not having the structure represented by the general formula (1) include those derived from monomers used in ordinary copolymerization. Examples thereof include a repeating unit derived from a monomer having an ethylenically unsaturated bond such as ethylene and styrene.

[Synthesis Method of Compound Represented by General Formula (1)]
The compound represented by the general formula (1) can be synthesized by combining known reactions. For example, it can be synthesized according to the following scheme.

R in the above formula is the same as the definition of R ^{1 to} R ^{6 in} the general formula (1). The above scheme shows a method for synthesizing compounds in which R ^{1 to} R ⁶ are all the same. X represents a halogen atom, and examples thereof include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a chlorine atom and a bromine atom are preferable.
The reaction in the above scheme is an application of a known coupling reaction, and known reaction conditions can be appropriately selected and used. For example, it can be synthesized by using NaH in DMF. The compound represented by the general formula (1) can also be synthesized by combining other known synthesis reactions.

[Utilization of compound represented by general formula (1)]
The compound represented by the general formula (1) is useful as a charge transport material. In particular, it is useful as a host material in consideration of use in combination with a light-emitting material that is a dopant. A thin film containing both the compound represented by the general formula (1) and a light emitting material can realize high light emission efficiency and luminance. The compound represented by the general formula (1) is particularly preferable in that it can realize high blue light emission efficiency and luminance when used in combination with a blue light emitting material. In order to realize high luminous efficiency and luminance in combination with such a blue light emitting material, it is necessary that the T1 level is high and the band gap is large. In general, a material having a high T1 level has a problem of poor thermal stability. The cyclotriphosphazene compound described in Non-Patent Document 1 (Chem. Mater., 2011, 23 (22), 4947-4953) also has a high T1 level, but the thermal stability is sufficiently satisfactory. It was not expensive. A solution to this has not been shown so far, but the compound represented by the general formula (1) proposed by the present invention has not only a high T1 level but also an excellent feature of high thermal stability. ing. The thermal decomposition temperature of the compound represented by the general formula (1) is preferably 330 ° C. or higher, more preferably 350 ° C. or higher, and further preferably 380 ° C. or higher. The thermal decomposition temperature here is a temperature at which a weight loss of 5% by weight or more is observed when the compound is heated.

  Since the compound represented by the general formula (1) has high thermal stability, it has an advantage of high applicability to thin film formation and organic light emitting device manufacturing processes. In addition, the compound represented by the general formula (1) can be made relatively low in molecular weight, and therefore has suitability for production because it is easily sublimated. For example, hexaphenylcyclotriphosphazene substituted with six carbazol-9-yl groups as described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2011-525047) is inferior in sublimation property, so that it is an actual industrial field. Application range is limited, and industrial utility is low.

  The compound represented by the general formula (1) has the above-described characteristics and also has a characteristic that high luminous efficiency and luminance can be realized when a thin film is formed together with a light-emitting material. The compound represented by the general formula (1) has a sufficiently deep HOMO energy level. For example, the energy level of HOMO is clearly deeper than that of hexaphenylcyclotriphosphazene substituted with the above six carbazol-9-yl groups. For this reason, the band gap represented by the general formula (1) is relatively large and is extremely effective as a host material for the blue light-emitting material. The band gap of the compound represented by the general formula (1) is preferably 3.0 eV or more, more preferably 3.5 eV or more, and further preferably 3.8 eV or more.

  The light emitting material used in combination with the compound represented by the general formula (1) may be a phosphorescent light emitting material, a fluorescent light emitting material, or a material that emits delayed fluorescence. Good. In particular, when combined with a light emitting material that emits delayed fluorescence (delayed phosphor), it is possible to dramatically increase the light emission efficiency and the luminance. The principle will be described below by taking an organic electroluminescence element as an example.

  In an organic electroluminescence element, carriers are injected into a light emitting material from both positive and negative electrodes to generate an excited light emitting material and emit light. In general, in the case of a carrier injection type organic electroluminescence element, 25% of the generated excitons are excited to the excited singlet state, and the remaining 75% are excited to the excited triplet state. Therefore, the use efficiency of energy is higher when phosphorescence, which is light emission from an excited triplet state, is used. However, since the excited triplet state has a long lifetime, energy saturation occurs due to saturation of the excited state and interaction with excitons in the excited triplet state, and in general, the quantum yield of phosphorescence is often not high. On the other hand, the delayed fluorescent material transitions to the excited triplet state due to intersystem crossing, etc., and then crosses back to the excited singlet state due to triplet-triplet annihilation or absorption of thermal energy, and emits fluorescence. To do. In the organic electroluminescence device, it is considered that a thermally activated delayed fluorescent material by absorption of thermal energy is particularly useful. When a delayed fluorescent material is used for the organic electroluminescence element, excitons in the excited singlet state emit fluorescence as usual. On the other hand, excitons in the excited triplet state absorb heat generated by the device and cross between the excited singlets to emit fluorescence. At this time, since the light is emitted from the excited singlet, the light is emitted at the same wavelength as the fluorescence, but the light lifetime (luminescence lifetime) generated by the reverse intersystem crossing from the excited triplet state to the excited singlet state is normal. Since the fluorescence becomes longer than the fluorescence and phosphorescence, it is observed as fluorescence delayed from these. This can be defined as delayed fluorescence. If such a heat-activated exciton transfer mechanism is used, the ratio of the compound in an excited singlet state, which normally generated only 25%, is increased to 25% or more by absorbing thermal energy after carrier injection. It can be raised. If a compound that emits strong fluorescence and delayed fluorescence even at a low temperature of less than 100 ° C is used, the heat of the device will sufficiently cause intersystem crossing from the excited triplet state to the excited singlet state and emit delayed fluorescence. Efficiency can be improved dramatically.

The light emitting material that can be used in combination with the compound represented by the general formula (1) is preferably a blue light emitting material, but a light emitting material that emits light of other colors may be used in combination. Conventionally known materials can be used as the blue light emitting material. Examples thereof include coumarin, perylene, pyrene, anthracene, p-bis (2-phenylethenyl) benzene, and derivatives thereof. As specific light emitting materials that can be used in combination with the compound represented by the general formula (1), the following compounds can be preferably exemplified.

[Organic light emitting device]
By using the compound represented by the general formula (1) of the present invention as a charge transporting material or a host material of a light emitting layer, an excellent organic photoluminescence element (organic PL element), organic electroluminescence element (organic EL element), etc. An organic light emitting device can be provided. At this time, the compound represented by the general formula (1) of the present invention may have a function of assisting light emission of another light emitting material included in the light emitting layer as a so-called assist dopant. That is, the compound represented by the general formula (1) of the present invention contained in the light emitting layer includes the lowest excitation singlet energy level of the host material contained in the light emitting layer and the lowest excitation of other light emitting materials contained in the light emitting layer. It may have the lowest excited singlet energy level between singlet energy levels.
The organic photoluminescence element has a structure in which at least a light emitting layer is formed on a substrate. The organic electroluminescence element has a structure in which an organic layer is formed at least between an anode, a cathode, and an anode and a cathode. The organic layer includes at least a light emitting layer, and may consist of only the light emitting layer, or may have one or more organic layers in addition to the light emitting layer. Examples of such other organic layers include a hole transport layer, a hole injection layer, an electron blocking layer, a hole blocking layer, an electron injection layer, an electron transport layer, and an exciton blocking layer. The hole transport layer may be a hole injection / transport layer having a hole injection function, and the electron transport layer may be an electron injection / transport layer having an electron injection function. A specific example of the structure of an organic electroluminescence element is shown in FIG. In FIG. 1, 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a hole transport layer, 5 is a light emitting layer, 6 is an electron transport layer, and 7 is a cathode.
Below, each member and each layer of an organic electroluminescent element are demonstrated. In addition, description of a board | substrate and a light emitting layer corresponds also to the board | substrate and light emitting layer of an organic photo-luminescence element.

(substrate)
The organic electroluminescence device of the present invention is preferably supported on a substrate. The substrate is not particularly limited and may be any substrate conventionally used for organic electroluminescence elements. For example, a substrate made of glass, transparent plastic, quartz, silicon, or the like can be used.

(anode)
As the anode in the organic electroluminescence element, an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (4 eV or more) is preferably used. Specific examples of such electrode materials include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ —ZnO) capable of forming a transparent conductive film may be used. For the anode, a thin film may be formed by vapor deposition or sputtering of these electrode materials, and a pattern of a desired shape may be formed by photolithography, or when pattern accuracy is not so high (about 100 μm or more) ), A pattern may be formed through a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material. Or when using the material which can be apply | coated like an organic electroconductivity compound, wet film-forming methods, such as a printing system and a coating system, can also be used. When light emission is extracted from the anode, it is desirable that the transmittance be greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less. Further, although the film thickness depends on the material, it is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

(cathode)
On the other hand, as the cathode, a material having a low work function (4 eV or less) metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof as an electrode material is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. Among these, from the point of durability against electron injection and oxidation, a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function value than this, for example, a magnesium / silver mixture, Suitable are a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, a lithium / aluminum mixture, aluminum and the like. The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. In order to transmit the emitted light, if either one of the anode or the cathode of the organic electroluminescence element is transparent or translucent, the emission luminance is advantageously improved.
In addition, by using the conductive transparent material mentioned in the description of the anode as a cathode, a transparent or semi-transparent cathode can be produced. By applying this, an element in which both the anode and the cathode are transparent is used. Can be produced.

(Light emitting layer)
The light emitting layer is a layer that emits light after excitons are generated by recombination of holes and electrons injected from each of the anode and the cathode, and the light emitting material may be used alone for the light emitting layer. , Preferably including a luminescent material and a host material. As a host material, 1 type (s) or 2 or more types selected from the compound group represented by General formula (1) can be used. In order for the organic electroluminescent device and the organic photoluminescent device of the present invention to exhibit high luminous efficiency, it is important to confine singlet excitons and triplet excitons generated in the light emitting material in the light emitting material. Therefore, it is preferable to use a host material represented by the general formula (1) in addition to the light emitting material in the light emitting layer. As the host material, an organic compound in which at least one of excited singlet energy and excited triplet energy has a value higher than that of the light-emitting material can be used. As a result, singlet excitons and triplet excitons generated in the light emitting material can be confined in the molecule of the light emitting material, and the light emission efficiency can be sufficiently extracted. However, even if singlet excitons and triplet excitons cannot be sufficiently confined, there are cases where high luminous efficiency can be obtained, so that host materials that can achieve high luminous efficiency are particularly limited. And can be used in the present invention. In the organic light-emitting device or organic electroluminescence device of the present invention, light emission is generated from the light-emitting material contained in the light-emitting layer. This luminescence may be any of phosphorescence, fluorescence, and delayed fluorescence, and may include a plurality of these. However, light emission from the host material may be partly or partly emitted.
When the host material is used, the amount of the light emitting material contained in the light emitting layer is preferably 0.1% by weight or more, more preferably 1% by weight or more, and 50% by weight or less. It is preferably 20% by weight or less, more preferably 10% by weight or less.
The host material in the light-emitting layer is preferably an organic compound that has a hole transporting ability and an electron transporting ability, prevents the emission of longer wavelengths, and has a high glass transition temperature.

(Injection layer)
The injection layer is a layer provided between the electrode and the organic layer for lowering the driving voltage and improving the luminance of light emission, and includes a hole injection layer and an electron injection layer, Further, it may be present between the cathode and the light emitting layer or the electron transport layer. The injection layer can be provided as necessary.

(Blocking layer)
The blocking layer is a layer that can prevent diffusion of charges (electrons or holes) and / or excitons existing in the light emitting layer to the outside of the light emitting layer. The electron blocking layer can be disposed between the light emitting layer and the hole transport layer and blocks electrons from passing through the light emitting layer toward the hole transport layer. Similarly, a hole blocking layer can be disposed between the light emitting layer and the electron transporting layer to prevent holes from passing through the light emitting layer toward the electron transporting layer. The blocking layer can also be used to block excitons from diffusing outside the light emitting layer. That is, each of the electron blocking layer and the hole blocking layer can also function as an exciton blocking layer. The term “electron blocking layer” or “exciton blocking layer” as used herein is used in the sense of including a layer having the functions of an electron blocking layer and an exciton blocking layer in one layer.

(Hole blocking layer)
The hole blocking layer has a function of an electron transport layer in a broad sense. The hole blocking layer has a role of blocking holes from reaching the electron transport layer while transporting electrons, thereby improving the recombination probability of electrons and holes in the light emitting layer. As the material for the hole blocking layer, the material for the electron transport layer described later can be used as necessary.

(Electron blocking layer)
The electron blocking layer has a function of transporting holes in a broad sense. The electron blocking layer has a role to block electrons from reaching the hole transport layer while transporting holes, thereby improving the probability of recombination of electrons and holes in the light emitting layer. .

(Exciton blocking layer)
The exciton blocking layer is a layer for preventing excitons generated by recombination of holes and electrons in the light emitting layer from diffusing into the charge transport layer. It becomes possible to efficiently confine in the light emitting layer, and the light emission efficiency of the device can be improved. The exciton blocking layer can be inserted on either the anode side or the cathode side adjacent to the light emitting layer, or both can be inserted simultaneously. That is, when the exciton blocking layer is provided on the anode side, the layer can be inserted adjacent to the light emitting layer between the hole transport layer and the light emitting layer, and when inserted on the cathode side, the light emitting layer and the cathode Between the luminescent layer and the light-emitting layer. Further, a hole injection layer, an electron blocking layer, or the like can be provided between the anode and the exciton blocking layer adjacent to the anode side of the light emitting layer, and the excitation adjacent to the cathode and the cathode side of the light emitting layer can be provided. Between the child blocking layer, an electron injection layer, an electron transport layer, a hole blocking layer, and the like can be provided. When the blocking layer is disposed, at least one of the excited singlet energy and the excited triplet energy of the material used as the blocking layer is preferably higher than the excited singlet energy and the excited triplet energy of the light emitting material.

(Hole transport layer)
The hole transport layer is made of a hole transport material having a function of transporting holes, and the hole transport layer can be provided as a single layer or a plurality of layers.
The hole transport material has any one of hole injection or transport and electron barrier properties, and may be either organic or inorganic. Known hole transport materials that can be used include, for example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, carbazole derivatives, indolocarbazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, Examples include amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers. An aromatic tertiary amine compound and an styrylamine compound are preferably used, and an aromatic tertiary amine compound is more preferably used.

(Electron transport layer)
The electron transport layer is made of a material having a function of transporting electrons, and the electron transport layer can be provided as a single layer or a plurality of layers.
The electron transport material (which may also serve as a hole blocking material) may have a function of transmitting electrons injected from the cathode to the light emitting layer. Examples of the electron transport layer that can be used include nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide oxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives, and the like. Furthermore, in the above oxadiazole derivative, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as an electron transport material. Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.

  When producing an organic electroluminescent element, the compound represented by the general formula (1) may be used as a host material for the light emitting layer, or may be used as a charge transport material for other organic layers. In that case, the compound represented by General formula (1) used for a light emitting layer and the compound represented by General formula (1) used for layers other than a light emitting layer may be same or different. For example, the compound represented by the general formula (1) may be used for the injection layer, blocking layer, hole blocking layer, electron blocking layer, exciton blocking layer, hole transporting layer, electron transporting layer, and the like. . The method for forming these layers is not particularly limited, and the layer may be formed by either a dry process or a wet process.

Below, the preferable material which can be used for an organic electroluminescent element is illustrated concretely. However, the material that can be used in the present invention is not limited to the following exemplary compounds. Moreover, even if it is a compound illustrated as a material which has a specific function, it can also be diverted as a material which has another function. In the structural formulas of the following exemplary compounds, R and R _{2 to} R ₇ each independently represent a hydrogen atom or a substituent. n represents an integer of 3 to 5.

  First, specific examples of compounds that can be used as the host material of the light emitting layer when the compound represented by the general formula (1) is used in a layer other than the light emitting layer are given.

  Next, examples of preferable compounds that can be used as the hole injection material will be given.

  Next, examples of preferred compounds that can be used as a hole transport material are listed.

  Next, examples of preferable compounds that can be used as an electron blocking material are given.

  Next, preferred compound examples that can be used as a hole blocking material are listed.

  Next, examples of preferable compounds that can be used as an electron transporting material will be given.

  Next, examples of preferable compounds that can be used as the electron injection material are given.

  Furthermore, preferable compound examples are given as materials that can be added. For example, adding as a stabilizing material can be considered.

The organic electroluminescence device produced by the above-described method emits light by applying an electric field between the anode and the cathode of the obtained device. At this time, if the light is emitted by excited singlet energy, light having a wavelength corresponding to the energy level is confirmed as fluorescence emission and delayed fluorescence emission. In addition, in the case of light emission by excited triplet energy, a wavelength corresponding to the energy level is confirmed as phosphorescence. Since normal fluorescence has a shorter fluorescence lifetime than delayed fluorescence, the emission lifetime can be distinguished from fluorescence and delayed fluorescence.
On the other hand, with respect to phosphorescence, in ordinary organic compounds such as the compounds of the present invention, the excited triplet energy is unstable and is converted into heat and the like, and the lifetime is short and it is immediately deactivated. In order to measure the excited triplet energy of a normal organic compound, it can be measured by observing light emission under extremely low temperature conditions.

  The organic electroluminescence element of the present invention can be applied to any of a single element, an element having a structure arranged in an array, and a structure in which an anode and a cathode are arranged in an XY matrix. According to the present invention, an organic light emitting device with greatly improved light emission efficiency can be obtained by containing the compound represented by the general formula (1) in the light emitting layer. The organic light emitting device such as the organic electroluminescence device of the present invention can be further applied to various uses. For example, it is possible to produce an organic electroluminescence display device using the organic electroluminescence element of the present invention. For details, see “Organic EL Display” (Ohm Co., Ltd.) written by Shizushi Tokito, Chiba Adachi and Hideyuki Murata. ) Can be referred to. In particular, the organic electroluminescence device of the present invention can be applied to organic electroluminescence illumination and backlights that are in great demand.

  The features of the present invention will be described more specifically with reference to test examples and examples. The following materials, processing details, processing procedures, and the like can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below. The evaluation of the light emission characteristics was performed using a semiconductor parameter analyzer (Agilent Technology: E5273A), an optical power meter measurement device (Newport: 1930C), an optical spectrometer (Ocean Optics: USB2000), and a streak camera. (C4334 type manufactured by Hamamatsu Photonics Co., Ltd.) was used as appropriate.

(Test Example 1) Evaluation of thermal stability About each of compound 1, mCP, and three cyclotriphosphazene compounds whose specific structures are described in Non-Patent Document 1 (compounds CP1, CP2, and CP3 described later) The decomposition temperature was measured by gradually increasing the temperature and confirming the temperature at which a 5% weight loss was observed. As a result, the decomposition temperature of Compound 1 was extremely high at 474 ° C., whereas mCP was 55 ° C. In addition, it is reported that the decomposition temperature of the cyclotriphosphazene compound of Non-Patent Document 1 is 280 to 330 ° C. From the above, it was confirmed that the thermal stability of the compound 1 of the present invention was extremely high.

Test Example 2 Measurement of T1 Level A methylene chloride solution of compound 1 (concentration 10 ⁻⁴ mol / L) was cooled to 77 ° K, and a PL spectrum was measured. The energy of the peak value on the shortest wavelength side of the PL spectrum was calculated and used as the T1 level (lowest excited triplet energy level) of the compound. The T1 level of Compound 1 was 3.00 eV (HOMO: 6.48 eV, LUMO: 2.52 eV). On the other hand, Appl. Phys. Lett., 2003, 82, 2422 reported that the T1 level of mCP is 2.9 eV (HOMO: 5.9 eV, LUMO: 2.4 eV).

1. Fabrication and evaluation of organic photoluminescence devices (thin films)
Example 1
A thin film having a concentration of 2CzCN of 3.0 wt% is obtained by depositing Compound 1 and 2CzCN from different deposition sources on a silicon substrate by a vacuum deposition method under a vacuum degree of 5.0 × 10 ⁻⁴ Pa. An organic photoluminescence device was formed at a thickness of 100 nm at 0.3 nm / second. FIG. 2 shows the result of measuring the emission spectrum of the produced organic photoluminescence device using ultraviolet excitation light. The photoluminescence quantum efficiency was 66.0% under the atmosphere and 84.8% under the nitrogen atmosphere.

2. Preparation and evaluation of organic electroluminescence device (Example 2)
Each thin film was laminated at a vacuum degree of 5.0 × 10 ⁻⁴ Pa by a vacuum deposition method on a glass substrate on which an anode made of indium tin oxide (ITO) having a thickness of 100 nm was formed. First, α-NPD was formed to a thickness of 35 nm on ITO, and mCP was formed to a thickness of 10 nm thereon. Next, Compound 1 and 2CzCN were co-evaporated from different vapor deposition sources to form a 20 nm thick layer as a light emitting layer. At this time, the concentration of 2CzCN was set to 3.0% by weight. Next, PPT was formed to a thickness of 40 nm, LiF was further vacuum-deposited to 0.8 nm, and then aluminum (Al) was evaporated to a thickness of 80 nm to form a cathode, whereby an organic electroluminescent element was obtained.
The emission spectrum of the produced organic electroluminescence element is shown in FIG. 3, the current density-voltage-luminance characteristic is shown in FIG. 4, and the current density-external quantum efficiency characteristic is shown in FIG. The maximum luminance was 18805 cd / m ² and the external quantum efficiency was very high at 14.9%. Assuming that an ideal organic electroluminescence device balanced using a fluorescent material having a light emission quantum efficiency of 100% is prototyped, if the light extraction efficiency is 20 to 30%, the external quantum efficiency of fluorescent light emission is 5 -7.5%. This value is generally regarded as a theoretical limit value of the external quantum efficiency of an organic electroluminescence device using a fluorescent material. The organic electroluminescence device of the present invention using Compound 1 is extremely excellent in that high external quantum efficiency exceeding the theoretical limit value is realized.

(Comparative Example 1)
An organic electroluminescence device was prepared in the same manner as in Example 2 using mCP instead of Compound 1, and the characteristics were evaluated in the same manner. The emission spectrum is shown in FIG. 3, the current density-voltage-luminance characteristic is shown in FIG. 4, and the current density-external quantum efficiency characteristic is shown in FIG. The maximum luminance was 16524 cd / m ² and the external quantum efficiency was 11.8%.
It was confirmed that the use of Compound 1 over mCP can provide an excellent organic electroluminescence device.

(Comparative Example 2)
An organic electroluminescence device was prepared in the same manner as in Example 2 using tBuCzPO instead of Compound 1, and the characteristics were evaluated in the same manner. FIG. 6 shows current density-voltage-luminance characteristics, and FIG. 7 shows current density-external quantum efficiency characteristics. The maximum luminance was 6436 cd / m ² and the external quantum efficiency was 12.8%.
It was confirmed that the use of Compound 1 over tBuCzPO can provide an excellent organic electroluminescence device.

(Example 3)
Each thin film was laminated at a vacuum degree of 5.0 × 10 ⁻⁴ Pa by a vacuum deposition method on a glass substrate on which an anode made of indium tin oxide (ITO) having a thickness of 100 nm was formed. First, α-NPD was formed to a thickness of 35 nm on ITO, and mCP was formed to a thickness of 10 nm thereon. Next, Compound 1 and 4CzIPN were co-evaporated from different vapor deposition sources to form a 20 nm thick layer as a light emitting layer. At this time, the concentration of 4CzIPN was 3.0% by weight. Next, PPT was formed to a thickness of 40 nm, LiF was further vacuum-deposited to 0.8 nm, and then aluminum (Al) was evaporated to a thickness of 80 nm to form a cathode, whereby an organic electroluminescent element was obtained.
An emission spectrum of the produced organic electroluminescence element is shown in FIG. 8, current density-voltage-luminance characteristics are shown in FIG. 9, and current density-external quantum efficiency characteristics are shown in FIG. The maximum luminance was 54141 cd / m ² , and the external quantum efficiency was extremely high at 17.8%.

(Comparative Example 3)
An organic electroluminescence device was prepared in the same manner as in Example 3 using mCP instead of Compound 1, and the characteristics were evaluated in the same manner. The emission spectrum is shown in FIG. 8, the current density-voltage-luminance characteristic is shown in FIG. 9, and the current density-external quantum efficiency characteristic is shown in FIG. The maximum luminance was 49176 cd / m ² and the external quantum efficiency was 17.7%.
It was confirmed that the use of Compound 1 over mCP can provide an excellent organic electroluminescence device.

  The compound represented by the general formula (1) is useful as a charge transport material. It is also useful as a host material when a light emitting material is used as a dopant. For this reason, the organic light emitting element using the compound represented by General formula (1) can implement | achieve high luminous efficiency and brightness | luminance. Therefore, the present invention has high industrial applicability.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Hole injection layer 4 Hole transport layer 5 Light emitting layer 6 Electron transport layer 7 Cathode

Claims (15)

A charge transport material comprising a compound represented by the following general formula (1).

[In General Formula (1), R ^{1 to} R ⁶ are each independently a group represented by the following General Formula (2).

[In the general formula (2), R ⁷ represents a substituted or unsubstituted aryl group or a substituted or unsubstituted aralkyl group. R ^{11 to} R ¹⁵ each independently represents a hydrogen atom or a substituent. R ⁷ and R ¹¹ , R ¹¹ and R ¹² , R ¹² and R ¹³ , R ¹³ and R ¹⁴ , and R ¹⁴ and R ¹⁵ may be bonded to each other to form a cyclic structure. ] The charge transport material according to claim 1, wherein R ^{1 to} R ^{6 in} the general formula (1) are all the same. The charge transport material according to claim 1 or 2, wherein R ^{1 to} R ^{6 in} the general formula (1) are groups represented by any one of the following general formulas (3) to (7).

[In the general formulas (3) to (7), R ^{21 to} R ³⁸ , R ^{41 to} R ⁴⁸ , R ^{51 to} R ⁵⁸ , R ^{61 to} R ⁶⁵ , R ^{71 to} R ⁷⁹ are each independently a hydrogen atom or a substituent. Represents a group. R ²¹ and R ²² , R ²² and R ²³ , R ²³ and R ²⁴ , R ²⁴ and R ²⁵ , R ²⁵ and R ²⁶ , R ²⁶ and R ²⁷ , R ²⁷ and R ²⁸ , R ²⁸ and R ²⁹ , R ²⁹ and R ^30, R ³¹ and R ^32, R ³² and R ^33, R ³³ and R ^34, R ³⁵ and R ^36, R ³⁶ and R ^37, R ³⁷ and R ^38, R ⁴¹ and R ^42, R ⁴² and R ⁴³ , R ⁴³ and R ⁴⁴ , R ⁴⁵ and R ⁴⁶ , R ⁴⁶ and R ⁴⁷ , R ⁴⁷ and R ⁴⁸ , R ⁵¹ and R ⁵² , R ⁵² and R ⁵³ , R ⁵³ and R ⁵⁴ , R ⁵⁵ and R ⁵⁶ , ^R56 and ^R57 , ^R57 and ^R58 , ^R61 and ^R62 , ^R62 and ^R63 , ^R63 and ^R64 , ^R64 and ^R65 , ^R54 and ^R61 , ^R55 and ^R65 , ^R71 And R ⁷² , R ⁷² and R ⁷³ , R ⁷³ and R ⁷⁴ , R ⁷⁴ and R ⁷⁵ , R ⁷⁶ and R ⁷⁷ , R ⁷⁷ and R ⁷⁸ , R ⁷⁸ and R ⁷⁹ are bonded to each other to form a cyclic structure. May be. ] The charge transport material according to claim 3, wherein R ^{1 to} R ^{6 in} the general formula (1) are groups represented by the general formula (3). The charge transport material according to claim 3 or 4, wherein R ^{1 to} R ^{6 in} the general formula (1) are groups represented by the following general formula (8).

[In General formula (8), R < ²¹ > -R < ²⁴ >, R < ²⁷ > -R < ³⁰ > represents a hydrogen atom or a substituent each independently. R ²¹ and R ²² , R ²² and R ²³ , R ²³ and R ²⁴ , R ²⁷ and R ²⁸ , R ²⁸ and R ²⁹ , and R ²⁹ and R ³⁰ may be bonded to each other to form a cyclic structure. ] The charge transport material according to claim 5, comprising a compound having the following structure.

[In the above structure, the hydrogen atom may be substituted with a substituent. ]   A host material comprising the charge transport material according to claim 1.   The host material according to claim 7, which is used for a blue light emitting material.   A thin film comprising the host material according to claim 7 and a light emitting material.   The thin film according to claim 9, wherein the light emitting material is a blue light emitting material.   An organic light emitting device using the charge transport material according to claim 1.   The organic light emitting device according to claim 11, wherein the charge transport material is used as a host material in a light emitting layer.   The organic light-emitting element according to claim 11, which emits phosphorescence.   The organic light-emitting device according to claim 11, which emits delayed fluorescence.   It is an organic electroluminescent element, The organic light emitting element of any one of Claims 11-14 characterized by the above-mentioned.

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